A connected DC/DC converter for use in the automotive field may be designed with a storage inductor which according to a control, for example a pulse width modulation signal, is short-circuited between a supply potential and a ground potential, using a switch which switches to ground. After the short circuit is interrupted, the charged storage inductor causes current to flow into an output capacitor, which provides an output voltage. The level of the output voltage may be set as a function of the pulse duty factor of the pulse width modulation signal which is used to activate the switch which switches to ground.
To improve the electromagnetic compatibility (EMC), in particular to reduce the conducted emissions on the supply voltage lines and the output lines, LC filters are generally necessary in each case. The output capacitor as well as the capacitors of the input-side and output-side LC filters are connected to the supply voltage and the output voltage, respectively, so that these capacitors divert the interferences, i.e., changes in the supply voltage level from high supply potential to ground potential. When electrolytic capacitors are used this has the disadvantage that, on account of the permanent direct connection of the DC/DC converter to the vehicle power supply, high effective currents result due to the ripple in the supply voltage. The electrolytic capacitors must therefore be designed for these high effective currents, which requires use of expensive capacitors.
Ceramic capacitors, which may be used instead of electrolytic capacitors, may fracture in the event of malfunction. These ceramic fractures result in short circuits between layers in the ceramic capacitors, as the result of which fault currents and power losses in the capacitors may occur.
Since in conventional DC/DC converters the capacitors are generally situated between the high supply potential and the ground potential, permanent current flows may arise overall which have an adverse effect on the components of the DC/DC converter which are used, and which subject the power supply network, in the case of a motor vehicle, the vehicle power supply, to unnecessary load.